Viscosimeter bath refrigeration unit



Sept. 13, 1955 P. LAWLER, JR

VISCOSIMETER BATH REFRIGERATION UNIT Filed June 5, 1955 COMPRE$SOR CHPI LLRRY METERING TUBE (2 i l J -1W5ATERJ 1 EVAFORATOR.

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Unite States Patent VISCOSIMETER BATH REFRIGERATION UNIT Paul Lawler, 3n, Bayonne, N. J.

Application June 5, 1953, Serial No. 359,729

2 Claims. (Cl. 257-4) This invention deals with a low temperature refrigeration unit specifically designed for cooling viscosimeter tubes and maintaining their temperature in this range with a high degree of accuracy. More specifically, it relates to a rnulti-cornpressor cascade cooling unit in which the evaporation of the primary refrigerant is carried under pressure in indirect cooling relation with the liquid secondary refrigerant before the latter is evaporated.

In determining accurately the viscosity of liquids, it is necessary to maintain the temperature of the viscosimeter within a very close range. Yet, it is often necessary to carry out the determination itself at a temperature anywhere from 212 F. to 40 F, or even as low as 100 F. Ordinary refrigerating systems are not adapted to provide adequate accuracy when such a wide zone of viscosimeter temperatures is employed. The present invention provides a simple and readily-controllable means for maintaining the viscosimeter temperature within such a wide zone with a remarkable degree of accuracy.

The invention may be more readily understood by reference to the accompanying drawing which depicts a preferred embodiment in diagrammatic form. In the drawing, numeral 1 designates the primary compressor into which is fed refrigerant vapor through line 2. The compressed refrigerant is discharged from compressor 1 through line 3 and into condenser 4 which may be air or water cooled. The cooled and liquefied refrigerant leaving the condenser through line 5 is discharged into receiver 6 for storage. From this receiver, the liquid refrigerant is drawn, when required, through line 7 and thermostatic expansion valve 8 and is expanded into pressure vessel 9 acting as the primary evaporator wherein the cooling action takes place. The thus-expanded refrigerant then is drawn out through line 10 which is pro vided with throttling constant pressure valves 11, preferably of the solenoid type, from which the vapor is led to intake line 2 of primary compressor 1. It will be noted that the primary refrigerating system is a separate, completely enclosed system which coacts with the secondary system which now will be described.

The secondary compressor 14 is the unit into which secondary refrigerant vapors are led through line 15, and compressed, after which the compressed vapors leaving through line 16 are discharged into oil separator 17 to trap any oil discharged from the compressor. The com pressed vapors leaving separator 17 through line 18 are cooled by water or air condenser 19. The thus-liquefied secondary refrigerant then is drawn through line 20 and through coil 21 which is cooled by indirect heat transfer by expansion of the primary refrigerant from valve 8 which discharges its expanded refrigerant into evaporator vessel 9.

The liquid secondary refrigerant, cooled by the gasified primary refrigerant, leaves cooling coil 21 via line 22 and then is expanded through capillary metering tube 21 into evaporator 24 wherein the cooling effect is transferred through a hath (not shown) to the adjacently disposed viscosimeter tube (not shown) immersed in the bath. The thus-expanded refrigerant vapor from evaporator 24 is finally led to inlet line 15 of secondary cornpressor 14 for further recycling.

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Thermostatic bulb 25 is connected by flexible tube 26 to valve 8 which also is directly connected by diaphragm and line 27 to pressure vessel 9. Strip or knife heater 28, having leads 29 and 30, is connected to a thermostatic switch (not shown) and a source of electric current. This heater is employed to prevent an overcooling surge or drift which may be caused by evaporator 24 when it is immersed in the cooling bath in which the viscosimeter also is immersed. Since heater 28 (and its accompanying thermostatic switch) are also immersed in the cooling bath, any cooling below the predetermined temperature will actuate the switch causing heater 28 to heat the bath and overcome said cooling surge.

The purpose of control valve 8 is to vaporize liquid refrigerant into cooling vessel 9 at a rate sufficient to maintain the predetermined constant temperature in vessel 9, and also to shut off the flow of liquid from line 7 if the presssure in vessel 9 exceeds the preset pressure. The primary refrigerant preferably is difluorodichloromethane (Freon 12), while the secondary refrigerant preferably is a lower boiling, readily vaporizable, normally gaseous liquid such as difiuoromonochloromethane (Freon 22).

Valves 11 are constant pressure throttling valves which may be of the solenoid type. These valves are adjusted to maintain a predetermined pressure in vessel 9, which would be about 30 p. s. i., if a temperature of 32 F. is to be maintained in vessel 9, using the refrigerant specified.

Tube 23 is a narrow metal capillary tube, the diameter and length of which are selected to give the desired flow rate of secondary liquid refrigerant into evaporator'24 to provide the desired temperature range in the cooling bath. All of the lines and vessels are of metal, preferabiy copper.

As already stated, by means of this cascade unit, it is possible to reach bath temperatures (produced by evaporator 24) of -40 F. to as low as l00 F., with an accuracy of about 0.01 F., thus making this unit particularly suitable for accurate viscosity determinations.

I claim:

1. A viscosimeter bath cooling unit comprising, in combination, a primary refrigeration system employing a liquefiable normally gaseous refrigerant, a compressor for compressing same, a refrigerant liquefying condenser, an evaporation vessel in which the refrigerant is evaporated, a thermostatically controlled expansion valve from which the refrigerant is expanded into said vessel for cooling said vessel and for recycle to the compressor, and which is controlled by thermostatic means at said vessel, a refrigerant throttling valve on the intake side of said compressor, and a secondary system also comprising a compressor for compressing a secondary refrigerant, and including a refrigerant liquefying condenser, and a coil disposed within said vessel of the primary system and in which said liquid secondary refrigerant may be cooled by indirect heat transfer with the vaporized primary refrigerant, a capillary metering tube through which the thus cooled liquid secondary refrigerant is passed and vaporized, a viscosimeter bath and an evaporator to be inserted in said viscosimeter bath and into which said vaporized secondary refrigerant is discharged for cooling said bath prior to compression by and for recycle to said secondary compressor.

2. A viscosimeter bath cooling unit according to claim 1 in which a thermostatically controlled heater is disposed in said bath adjacently to said secondary evaporator to counteract any overcooling occurring through operation of said evaporator.

Rooney Jan. 29, 1939 Gonzalez Mar. 18, 1941 

